Preparation of 1,3,5-triamino-2,4,6-trinitrobenzene from 3,5-dichloroanisole

ABSTRACT

Preparation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) from 3,5-dichloroanisole. Nitration of 3,5-dichloroanisole under relatively mild conditions gave 3,5-dichloro-2,4,6-trinitroanisole in high yield and purity. Ammonolysis of this latter compound gave the desired TATB. Another route to TATB was through the treatment of the 3,5-dichloro-2,4,6-trinitroanisole with thionyl chloride and dimethylformamide to yield 1,3,5-trichloro-2,4,6-trinitrobenzene. Ammonolysis of this product produced TATB.

The United States Government has rights in this invention pursuant toContract No. W-7405-ENG-36 between the U.S. Department of Energy and theUniversity of California.

This is a division of application Ser. No. 289,653, filed Dec. 21, 1988.

BACKGROUND OF THE INVENTION

The present invention relates generally to the preparation oftriaminotrinitrobenzene (TATB), and more specifically to the preparationof TATB from 3,5-dichloroanisole (DCA).

Triaminotrinitrobenzene is an explosive having unusual insensitivity,stability at high temperature, and respectable performance. It isinsoluble in organic solvents and has a melting point above 400° C. TATBwas prepared in 1887 from tribromotrinitrobenzene. It has also beenprepared on a laboratory scale from 2,4,6-trinitrotoluene throughselective reduction of the 4-nitro group, nitration topentanitroaniline, and then ammonolysis. Currently, the manufacture ofTATB (1) on a large scale begins with 1,3,5-trichlorobenzene (TCB, 2)which is nitrated to give 1,3,5-trichloro-2,4,6-trinitrobenzene (TCTNB,3) as shown in FIGS. 1a and 1b hereof. The nitration step requiressevere conditions of high temperature, long reaction time, and oleum,and results in significant quantities of by-products.

Accordingly, it is an object of the present invention to provide a moreefficient process for synthesizing TATB.

Additional objects, advantages and novel features of the invention willbe set forth in part in the description which follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and attained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

SUMMARY OF THE INVENTION

To achieve the foregoing and other objects and in accordance with thepurpose of the present invention, as embodied and broadly describedherein, the method of preparing TATB of this invention includes thesteps of nitrating 3,5-dichloroanisole to produce3,5-dichloro-2,4,6-trinitroanisole, and ammonolyzing the3,5-dichloro-2,4,6-trinitroanisole to yield TATB.

In a further aspect of the present invention, in accordance with itsobjects and purposes, the method of preparing TATB of this inventionincludes the steps of nitrating 3,5-dichloroanisole to produce3,5-dichloro-2,4,6-trinitroanisole, chlorinating the3,5-dichloro-2,4,6-trinitroanisole so produced to yield1,3,5-trichloro-2,4,6-trinitrobenzene, and ammonolyzing the1,3,5-trichloro-2,4,6-trinitrobenzene to yield TATB.

Benefits and advantages of the present invention include ease ofnitration of the starting materials, the purity of the nitratedintermediates, and the rapidity and high yield of the reaction. As aresult, development of a continuous process appears to be possible.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate two embodiments of the present inventionand, together with the description, serve to explain the principles ofthe invention. In the drawings:

FIG. 1 illustrates the present commercial, large-scale synthesis ofTATB. FIG. 1a shows the nitration of the starting material,1,3,5-trichlorobenzene (2) to the intermediate1,3,5-trichloro-4,6-trinitrobenzene (3), while FIG. 1b shows theammonolysis of this latter compound to TATB (1).

FIG. 2 illustrates the synthesis of TATB according to the teachings ofthe present invention. FIG. 2a shows the nitration of the startingmaterial, 3,5-dichloroanisole (4) to 3,5-dichloro-2,4,6-trinitroanisole(5), while FIG. 2b shows the ammonolysis of this latter compound to TATB(1). FIG. 2c shows an alternative path to reach the desired TATB. The3,5-dichloro-2,4,6-trinitroanisole (5) is first further chlorinated toyield 1,3,5-trichloro-2,4,6-trinitrobenzene, then ammonolyzed to yieldTATB (1) according to the reaction described in FIG. 1b hereof.

FIG. 3 illustrates the nitrated chlorobenzenes produced as a by-productfrom the commercial, large-scale synthesis currently employed andillustrated in FIG. 1 hereof.

FIG. 4 illustrates a bi-product from the synthesis according to theteachings of the present invention illustrated in FIG. 2 hereof.

DETAILED DESCRIPTION OF THE INVENTION

Briefly, the present invention teaches the preparation of1,3,5-triamino-2,4,6-trinitrobenzene, TATB, from the nitration of3,5-dichloroanisole under relatively mild conditions in high yield andpurity. The intermediate, 3,5-dichloro-2,4,6-trinitroanisole, is readilyammonolyzed to the TATB desired product. Another route is to firstchlorinate this intermediate to give1,3,5-trichloro-2,4,6-trinitrobenzene, which then may be ammonolyzed toproduce TATB.

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Turning to FIG. 1, the large-scale, commercialpreparation of TATB is illustrated. The conditions necessary to effectthe introduction of the third nitro group into the trichloro compoundstarting material 2 to produce 3 are quite severe. An excess of 90-95%nitric acid (4.35 moles per mole of 2) and 25-30% oleum (20 moles) areused at a reaction temperature of 150° C. with vigorous stirring for 2.5hours, as is described in "Method for the Production of High-PurityTriaminotrinitrobenzene," U.S. Pat. No. 4,032,377, issued to T. M.Benziger in June 1977. the teachings of which are hereby incorporated byreference herein. After quenching the mixture with water, the productwas isolated in 91% yield and 89% purity. The by-products were othernitrated chlorobenzenes, primarily 1,3,5-trichloro-2,4-dinitrobenzene(6) (3%), and 1,2,3,5-tetrachloro-4,6-dinitrobenzene (7 ) (8%) asillustrated in FIG. 3 hereof. The conversion was 0.80 mole of 3 per moleof 2. For subsequent ammonolysis of 3 to 1, it was unnecessary to removeeither 6 or 7, since both compounds are virtually unreactive towardammonia. The tetrachloro compound 7 was formed from the dinitrointermediate 6 and chlorine (or a chlorinating species) that had beengenerated by oxidation of 6. For the optimum conditions of time,temperature, and concentrations investigated, it was shown that aportion of the intermediate 6 (equivalent to approximately 0.03 mole permole of the starting material 2) was oxidized to give carbon dioxide(0.18 mole) and the active chlorine (0.09 mole), which then reacted withadditional 6 (equivalent to 0.09 mole of 2) to give compound 7 (0.09mole).

Nitration of starting material 4 would be expected to proceed morerapidly than nitration of compound 2 because of the activating effect ofthe methoxyl group on electrophilic aromatic substitution. The reactionillustrated in FIG. 2a hereof was indeed found to proceed with excellentyield at lower temperature (100° C.) without the necessity of an excessof nitric acid or the use of oleum. No by-product analogous to 7 wasdetected. Complete conversions of the starting material were obtainedwhen the excess of nitric acid was merely five percent over thestoichiometric amount. For this latter result, a temperature of 125°C.was employed, and the reaction allowed to proceed for two hours.However, the use of a minimum of nitric acid has a distinct advantagefor synthesis of the nitrogen-15 labeled analog.

Displacements of both the chloro and the methoxyl groups of 5 by ammoniaoccurred readily to give 1. Ammonolysis of reactions using limitedamounts of ammonia give a mixture of 1 and starting materials 3 or 5,with only very small quantities of mono- and di-amino compounds.However, from reactions in which mixtures of 3 and 5 were treated withlimited quantities of ammonia, it was found that 5 reacted several timesfaster than 3. For certain applications, it is desirable that TATB beproduced With a median particle size cf about 50 μm. Ammonolysis at lowtemperatures results in 1 precipitating as extremely small crystals.However extensive side reactions were found to occur when ammonolysis of5 was carried out at temperatures above 50° C. FIG. 4 shows theprincipal side reaction in the ammonolysis of 5. This reaction does notoccur at low temperatures since ammonium chloride is insoluble intoluene, and when better solvents for the chloride, such asdimethylformamide or dimethyl sulfoxide, are employed, or added to thetoluene, the yield of 1 is substantially reduced, even at lowtemperature. The material was thus of small size (90% of the particleswere smaller than 10 μm). However, the purity of 1, which was obtainedin yields greater than 95%, was unaffected by side reactions when theammonolysis reactions were conducted at ambient temperature and inrelatively nonpolar solvents.

Recrystallization of TATB is impractical on a large scale. When smallquantities having extremely high purity are desired, however, TATB maybe recrystallized from dimethyl sulfoxide or from diphenyl ether.

Direct conversion from 5 to 3 can be achieved in excellent yield andpurity when a stoichiometric amount of dimethyl formamide is employed.With catalytic amounts, the reaction is slow, and there is somereduction of nitro groups to azoxy. Although producing 3 from 5 requiresan additional step over its production from 2, the overall yield andconversion are higher, the product is of high purity (no by-productanalogous to 7), and conditions for the nitration of 4 are milder andoffer the possibility for a continuous process, with less waste beinggenerated.

Having generally described the invention, the specific embodimentshereof are demonstrated in the following examples.

EXAMPLE I

Preparation of 3,5-dichloro-2,4,6-trinitroanisole (5):3,5-dichloroanisole (35.4 g 0.20 mole) was added over a period of 2 min.to a stirred mixture of nitric acid (90%, 50 ml, 1.0 mol) and sulfuricacid (94%, 115 ml) in a flask cooled in an ice bath. The temperature ofthe mixture was found to rise to 50° C. After 3 min. the ice bath wasremoved, and the mixture was heated from 35° C. to 100° C. over a periodof 8 min. where it was held for 15 min. The mixture was then cooled toroom temperature and poured onto ice. The product was filtered, washedwith water, and dried (61.5 g, 98.6% yield). The melting point of theresulting compound was 94-95° C. (95-95.5° C. after recrystallizationfrom toluene-hexane).

EXAMPLE II

Preparation of 1,3,5-trichloro-2,4,6-trinitrobenzene (3):

Thionyl chloride (0.20 ml, 0.027 mol) and dimethylformamide (0.15 ml,0.022 mol) were added to a solution of 5 (0.624 g, 0.020 mol) in toluene(2 ml) at 50° C. The mixture was stirred and heated to 95° C. over aperiod of 15 min. and maintained at that temperature for another hour.The pale yellow solution was washed with water, dried over magnesiumsulfate, treated with activated carbon, filtered, and evaporated to givea cream-colored solid (0.600 g, 95% yield). The melting point of thematerial so obtained was 194-195° C. (195-196° C. afterrecrystallization from acetic acid).

EXAMPLE III

A. preparation of 1,3,5-triamino-2,4,6-trinitrobenzene (1) according toFIG. 2b hereof:

A solution of 5 (3.12 g, 0.010 mol) in toluene (40 ml) was placed in astainless-steel autoclave having a Teflon-covered stirring bar and thesystem evacuated to the vapor pressure of toluene (30-40 mm of Hg).Ammonia (5.5 mmol) was admitted to the autoclave over a period of 30min. during which time the temperature rose to about 30° C. Theautoclave was opened, the mixture filtered, and the bright yellowproduct was washed sequentially with toluene, hot water, and acetone,and dried (2.47 g, 96% yield).

B. Preparation of 1,3,5-triamino-2,4,6-trinitrobenzene (1) according toFIG. 2b hereof:

Ammonia was introduced over the surface of a vigorously stirred solutionof 5 (2.56 g, 8.2 mmol) in toluene (40 ml). After about 7 hours thesupernatant solution over the pale yellow precipitate became colorless,and analysis showed the absence of starting material and intermediates.The ammonia flow was halted, and the product was isolated as in A above(1.99 g, 94% yield). Recrystallization of TATB from either dimethylsulfoxide (5 g/l at 145° C.) or from diphenyl ether (2 g/l at 220° C.)removed trace impurities with essentially complete recovery of the TATB.

The foregoing description of two preferred embodiments of the inventionhas been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed, and obviously many modifications and variations arepossible in light of the above teaching. For example, in view of therapidity of the reactions involved in the synthesis of TATB according tothe teachings of the present invention, and the relatively mildconditions employed, development of a continuous process would beapparent to one having ordinary skill in the synthesis of explosivesafter studying the details of the subject disclosure. The embodimentswere chosen and described in order to best explain the principles of theinvention and its practical application to thereby enable others skilledin the art to best utilize the invention in various embodiments and withvarious modifications as are suited to the particular use contemplated.It is intended that the scope of the invention be defined by the claimsappended hereto.

What we claim is:
 1. A method for preparing1,3,5-triamino-2,4,6-trinitrobenzene from 3,5-dichloroanisole,comprising the steps of:a. nitrating 3,5-dichloroanisole to produce3,5-dichloro-2,4,6-trinitroanisole; and b. ammonolyzing3,5-dichloro-2,4,6-trinitroanisole.
 2. The method as described in claim1, wherein said step of nitrating 3,5-dichloroanisole includes the useof nitric acid and sulfuric acid.
 3. The method as described in claim 1,wherein said step of ammonolyzing the 3,5-dichloro-2,4,6-trinitroanisoleincludes the use of ammonia in toluene.